When dumping grain from a road train into a hopper a significant amount of dust is thrown up from the hopper the dust can "envelope" the road train and linger for some time. Mechanical dust retention systems have been designed to contain dust within the hopper so as to overcome or at least reduce this problem. A known dust retention system consists of a series of pressed steel doors hinged to a longitudinal beam which forms part of a grated floor structure through which the road train dumps the grain. Each of the steel doors is hinged at several points with a torsion spring acting on the door so as to urge it closed in an upward direction.
Although the known dust retention system is relatively inexpensive to manufacture it suffers from at least the following drawbacks:
i) the hinged doors rely on moving parts for operation which require frequent maintenance or replacement; PA1 ii) the hinged doors are, with the sound of grain impacting on the solid steel surface, relatively noisy; PA1 iii) the doors are difficult to install demanding a relatively large amount of downtime; PA1 iv) the doors are subject to corrosion thereby requiring cleaning and frequent maintenance; and, PA1 v) the rate of flow of particulate material is unacceptably restricted. PA1 a support member adapted to be mounted above the product vessel; and, PA1 a door including an engaging portion detachably mounted on the support member and retained in place by an adjustment means for adjusting the door to a desired angle with respect to the support member, the door also including a striking portion adjacent the engaging portion with at least a section of the striking portion being constructed of a resiliently flexible material; PA1 whereby, in use, product falling onto the striking portion causes the resiliently flexible material of the striking portion to be deflected by the weight of said product thereby forcing the door from a closed position, where dust is inhibited from escaping the product vessel, into an open position where the product passes across the door and into the product vessel, and thereafter the door, without the weight of said product, returning to the closed position under a bias force exerted by said resiliently flexible material. Preferably, the door is detachably mounted substantially above the support member.
Also, it is known to have flexible doors which flex under the weight of particulate material being dumped onto the flexible doors. It is difficult to correctly position the flexible doors for use at a desired angle to the floor structure. In addition the flexible doors often need adjustment or maintenance. There is therefore a need for a means of adjusting the flexible doors that also accommodates maintenance of the dust retention system.